/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.accept;

import java.util.Collections;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.http.MediaType;
import org.springframework.web.server.ServerWebExchange;

/**
 * Resolver that always resolves to a fixed list of media types. This can be
 * used as the "last in line" strategy providing a fallback for when the client
 * has not requested any media types.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class FixedContentTypeResolver implements RequestedContentTypeResolver {

    private static final Log logger = LogFactory.getLog(FixedContentTypeResolver.class);


    private final List<MediaType> mediaTypes;


    /**
     * Constructor with a single default {@code MediaType}.
     */
    public FixedContentTypeResolver(MediaType mediaType) {
        this(Collections.singletonList(mediaType));
    }

    /**
     * Constructor with an ordered List of default {@code MediaType}'s to return
     * for use in applications that support a variety of content types.
     * <p>Consider appending {@link MediaType#ALL} at the end if destinations
     * are present which do not support any of the other default media types.
     */
    public FixedContentTypeResolver(List<MediaType> mediaTypes) {
        this.mediaTypes = Collections.unmodifiableList(mediaTypes);
    }


    /**
     * Return the configured list of media types.
     */
    public List<MediaType> getContentTypes() {
        return this.mediaTypes;
    }


    @Override
    public List<MediaType> resolveMediaTypes(ServerWebExchange exchange) {
        if (logger.isDebugEnabled()) {
            logger.debug("Requested media types: " + this.mediaTypes);
        }
        return this.mediaTypes;
    }

}
